net-next: ethernet: mediatek: add CDM able to recognize the tag for DSA

The patch adds the setup for allowing CDM can recognize these packets with
carrying port-distinguishing tag. Otherwise, these tagging packets will be
handled incorrectly by CDM. The setup is also working out for general
untag packets as well.

Signed-off-by: Sean Wang <sean.wang@mediatek.com>
Signed-off-by: Landen Chao <Landen.Chao@mediatek.com>
Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Reviewed-by: Florian Fainelli <f.fainelli@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/ethernet/mediatek/mtk_eth_soc.c

@@ -1846,6 +1846,12 @@ static int mtk_hw_init(struct mtk_eth *eth)
 	/* GE2, Force 1000M/FD, FC ON */
 	mtk_w32(eth, MAC_MCR_FIXED_LINK, MTK_MAC_MCR(1));
 
+	/* Indicates CDM to parse the MTK special tag from CPU
+	 * which also is working out for untag packets.
+	 */
+	val = mtk_r32(eth, MTK_CDMQ_IG_CTRL);
+	mtk_w32(eth, val | MTK_CDMQ_STAG_EN, MTK_CDMQ_IG_CTRL);
+
 	/* Enable RX VLan Offloading */
 	mtk_w32(eth, 1, MTK_CDMP_EG_CTRL);
 

drivers/net/ethernet/mediatek/mtk_eth_soc.h

@@ -70,6 +70,10 @@
 /* Frame Engine Interrupt Grouping Register */
 #define MTK_FE_INT_GRP		0x20
 
+/* CDMP Ingress Control Register */
+#define MTK_CDMQ_IG_CTRL	0x1400
+#define MTK_CDMQ_STAG_EN	BIT(0)
+
 /* CDMP Exgress Control Register */
 #define MTK_CDMP_EG_CTRL	0x404